Polarized track circuit railway signaling apparatus



C. B. SHIELDS July 15, 1958 POLARIZED TRACK CIRCUIT RAILWAY SIGNALINGAPPARATUS 4 Sheets-Sheet 1 Filed Jan. 29, 1953 lxvvzwwgiz Charles B.Sbzelds.

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July 15, 1958 c. B SHIELDS POLARIZED TRACK CIRCUIT RAILWAY SIGNALINGAPPARATUS Filed Jan. 29. 1953 4 Sheets-Sheet 5 LB I INVENTOR. B NUhar'les 5. Shield; lll

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POLARIZED TRACK CIRCUIT RAILWAY SIGNALING APPARATUS Filed Jan. 29, 19534 Sheets-Sheet 4 1 when find: I zgqpzoackes' 1 Scgnal Stop.

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HIS ATTORIVF' United States Patent POLARIZED TRACK'CIRCUIT RAILWAYSIGNALING APPARATUS Charles B. Shields, Penn Township, Allegheny County,Pa., assignor to Westinghouse Air Brake Company, Wilmerding, Pa., acorporation of Pennsylvania Application January 29, 1953, SerialNo.-333,983

5 Claims. (Cl. 2463) My invention relates to railway trafiic Controllingapparatus and particularly to coded polarized track circuits applied tosingle track, two direction signaling systems. More particularly,myinvention relates to a signaling system of the above character inwhich the direction of trafiic is established by a code sent out from acentral traflic controlling station or by other suitable manual control.Accordingly, the directional control of the system embodying myinvention is not automatic as in the case of standard APB circuits.

The present invention is an improvement on the circuits shown anddescribed in United States Reissue Patent No. 22,841, granted to me onFebruary 11, 1947, for Railway Traffic Controlling Apparatus. Thenovelty in my present invention resides chiefly in using continuouspolarized code pulses for establishing the direction of traffic ratherthan using a singletransient code pulse as was employed in theabove-mentioned patent.

One object of my invention is to provide for thereversal of traflicdirection without the use of control line wires, by reversing thepolarity of the track circuit.

Another object of my inventionis'to provide directional locking betweenheadblock signals so that traffic direction cannot be reversed or theopposing headblock signal cleared while the section is'occupied by atrain.

' A further object of my invention is to provide for approachenergizati'on of the intermediate wayside signals by selecting thepolarity of the approach code.

Still --a further object of my invention is to dispense with all controlwires except the control wires necessary in-a centralized trafliccontrol system or other manual traflic control'and to provide a safe andeffective system of twodirection, singletrack signaling.

Yet another object of my invention is to make use of the same trackbattery which supplies the approach code energy for supplying thefeedback track energy upon a reversal of traffic direction.

According to my invention, I provide a pair of polarized track relays ateach end of each-track section selectively responsive to codes ofopposite polarity being transmitted from the-opposite end of the sectionby code transmitting means which, if a stretch of track is cleared forone direction of traflic, will supply code of one polarity and if thestretch is cleared for the opposite direction, the supplied code will beof the opposite'polarity. Upon the reversal of the polarity of the codebeing supplied at one endcfthe stretch, means controlled by the trackrelays cascade the polarity reversal .tothe otherend of thestr-etchwhereupon the codebeing suppliedrat the other end of the stretchreverses its polarity. This latter reversal of polarity is cascaded tothe first end of the stretch by means also including the track relays. Ifurther provide means for preventing the cascading of the reversal ofpolarity if the codes being supplied at each end .of each section arenot of the same relative polarity. This provides a directionallockingfeature.

The control of the direction of traffic overthe stretch and of'thedirectional locking of traflic in the stretch are 2,843,731 PatentedJuly 15, 1958 both accomplished through the medium of the track circuitsand are dependent only upon the polarity of the codes being supplied tothe'stretch. Accordingly, no line wires are necessary other than C. T.C. control wires or other manual control wires.

Other objects of my invention will appear herein-after as thecharacteristic features of construction and mode of operation of myinvention are described in detail.

-I shall describe one form of apparatus embodying my invention, and"shall then point out the novel features thereof in claims.

Figs. 1A, 1B, 1C and 1D, inclusive, of the accompanying drawings, whenplaced side 'by .side in consecutive order with Fig. 1A at the leftprovide a diagrammatic view showing one form of apparatus embodying myinvention.

Similar reference characters refer to similar parts in each of theseveral figures.

Referring llOWltO the drawings, there is shown a stretch of single trackmade up of rails 1 and 2, and thea'djoining ends of a Western and aneastern passing siding made up of rails 3 and 4 and 5 and .6,respectively. The stretch of single track and the sidings are dividedinto track sections 2T, 4T, 6AT, 6BT and ST by insulated joints 7 placedin the rails. The rails of the single track stretch that make up section21 are connected in multiple with the rails of the western passingsiding by a wire 8 and the frog arrangement, and the main track rails ofsection 8T are connected to the rails.;of the eastern passing siding bya wire '9 and the frog arrangement, to provide the usual and well-knownshunt fouling protection.

At the western headblock, shown in Fig. 1A, are provided eastboundsignals ZRAS and ZRBS and a westbound signal ZLS. Each of the signalsmaybe of any suitable type, and are here shown as the well-known colorlight type. Section 2T is provided with a conventional direct currenttrack circuit includinga track battery 2TB and a track relay ZTR. Acontrol lever L1 controls trafiic control relays WFS and EFS, the latterbeing located at the eastern headblock location. Since the means forcontrolling the traffic control relays forms no part of my invention,control lever Ll-and the line wires can 'be replaced with a lever ateach headblock location or by some form of centralized traffic control.

Coded current .is used to control the wayside signals. The current iscoded at difierent code rates according to different traffic conditions.In the three aspect system here shown, code rates of 180 and pulses perminute are employed. When 180 code is supplied to a track circuit, thewayside signals will display a green aspect indicating a clear track anda train is permitted to travel at its maximum permissive speed. When 75code-issupplied to the track circuit, the wayside signal will display ayellow aspect indicating that caution should be exercised by theengineer and thetrain should proceed at medium speed. When no energy isreceived by the track relay, the wayside signal will display a redaspect indicatingthat a train approaching the signal should come toastop.

Current for the operation of the apparatus other than the track circuitsis provided by suitable sources .of direct current, such .as thebatteriesLB shown. Each of the relays operated by coded energy is of thepolar biased type, having contacts which are picked up whenand only whencurrent flows through the relay winding in the .direction indicated bythe arrow thereon.

In Fig. 1A, a code transmitting relay 2WCTRis supplied with coded.energy from battery LB ,by ,theoperation of coders 75CT and 180CT. Codefollowing track relays 2ETR and ZWVRcontrol the supply of energy todecoding transformers.2ETT and ZWTT, respectively. Connected to awinding of transformer '2ETT is adeco'ding'unit lDU which is ofconventional design and will supply suflicient energy to cause a clearcontrol relay ZDR to pick up only when'the decoding unit is beingenergized at a code rate of 180 pulses per minute. An impulsetransformer W2 is also at times energized by a winding of eithertransformer ZETT or ZWTT, depending upon traffic conditions. The windingof each of the relays 2EHR and ZWVPR is connected to another winding ofdecoding transformers ZETT and ZWTT, respectively. Energy is supplied totrack section 4T by a track battery 4WTF, in response to the operationof the code transmitting relay ZWCTR.

A polar stick relay ZDSR controls in part a polar stick relay ZDSKR.These polar stick relays areof a conventional type Which, afterdeenergization, maintain their contacts in the position to which theywere last operated. These polar stick relays will, upon energization ofeither winding, operate their contacts in the direction from which thecurrent is flowing. The ZDSKR relay controls a reverse repeater relayZDSKRPR which is a conventional slow-release neutral relay. -A lever L2and contacts and 11 of a circuit controller operated by switch 1Wcontrol signal control relays ZRAHR and ZRBHR which in turn control anapproach locking relay ZRMSR and a time element relay ZTER. Alsoprovided at the western headblock location are in approach relay ZRARand a signal control relay ZLAHR.

At the intermediate signal location IS, as shown in Fig. 1B, are twosignals 4L5 and 40RS. Coders 75CT and 180CT control the supply of energyfrom battery LB to code transmitting relays 4ECTR and 4WCTR which inturn supply coded energy from track batteries 4ETB and 6AWTB to sections4T and 6AT, respectively. Code following track relays 4EVR, 4WTR, 4ETRand 4WVR control the supply of energy to decoding transformers 4ETT,4WTT, 6AETT and 6AWTT, respectively. A winding of each of transformers4ETT and 4WTT at times supplies coded energy to an impulse transformer4WWT and a winding of each of transformers 6AETT and 6AWTT at timessupplies coded energy to an impulse transformer 4EWT. A winding oftransformer 4WTT or a winding of transformer 6AETT, depending upontraffic conditions, supplies coded energy to decoding unit 180DU whichcontrols the supply of energy to a clear control relay 4DR.

Another winding of each of the decoding transformers 4ETT, 4WTT, 6AETTand 6AWTT is connected to a winding of code detecting relays 4EVPR,4WHR, 4EHR and 4WVPR, respectively. In addition, at the intermediatesignal location, there are provided a polar stick relay 4DSR, its normalrepeater relay 4DSNPR and its reverse repeater relay 4DSRPR. Relay 4DSR,in cooperation with relays 4DSNPR and 4DSRPR, functions to control thesupply of energy being coded by coders 180CT and 75CT to either relay4ECTR or 4WCTR. Furthermore, relay 4DSR also partially controls signals4LS and 4R5.

At the cut section location CS, shown in Fig. 1C, code transmittingrelays CECTR and CWCTR code the energy supplied from track batteries6AETB and 6BWTB, respectively, to sections 6AT and 6BT, respectively.Codefollowing track relays CEVR, CWTR, CETR and CWVR control the supplyof energy from battery LE to decoding transformers AETT, AWTT, BETT andBWTT, respectively. A winding of each of transformers AETT and AWTT attimes supplies energy to an impulse transformer CWWT and a winding ofeach of transformers BETT and BWTT at times supplies energy to animpulse transformer CEWT, depending upon trafiic conditions. Anotherwinding of each of transformers AETT, AWTT, BETT and BWTT is connectedto a winding of each of code detecting relays CEVPR, CWHR, CEHR andCWVPR, respectively. A polar stick relay CDSR controls the operation ofa normal repeater relay CDSNPR and a reverse repeater relay CDSRPR.

At the eastern headblock, shown in Fig. 1D, track sec- 4 tion ST isprovided with a conventional direct current neutral track circuitincluding a track battery 8TB and a track relay STR. A code transmittingrelay 6ECTR is supplied with coded energy from either coder 75CT orcoder 180CT, depending upon traffic conditions. Relay 6ECTR codes energysupplied from a track battery 6BETB to section 6BT, Code following trackrelays 6EVR and 6WTR govern the supply of energy from battery LB todecoding transformers 6ETT and 6W l'l respectively. Decoding unit 180DUis connected to a winding of transformer 6WTT and the decoding unit inturn controls relay 6DR. A separate winding of transformer 6ETT or 6WTTat times supplies energy to an impulse transformer E6, depending upontrafiic conditions. A winding of transformer 6ETT at time suppliesenergy to a code detecting relay 6EVPR and a winding of transformer 6WTTat times supplies energy to a code detecting relay 6WHR.

Also provided at the eastern headblock are two polar stick relays 6DSRand 6DSKR and a slow release normal repeater relay 6DSKNPR. A controllever L6 and contacts 12 and 13 of a circuit controller operated byswitch 5W control signal control relays 6LAHR and 6LBHR which in turncontrol signals 6LAS and 6LBS, respectively. An approach relay 6LAR andthe signal control relays 6LAHR and 6LBHR control an approach lockingrelay 6LMSR, and all of these relays control a time element relay 6TER.A signal control relay 6RAHR controls a signal 6RS.

Before proceeding with a detailed description of the operation of thesystem, it is desirable to define several terms which will be usedextensively in the following description. Normal codes, as herein used,are codes transmitted in a direction opposite to the establisheddirection of tralfic. tion to normal code. Codes of normal polarity arecodes which energize rail 1 positively and rail 2 negatively. Codes ofreverse polarity energize the rails 1 and 2 opposite to codes of normalpolarity.

As shown, the system is set up for a westbound traffic movement. LeverL1 is in its W position thereby energizing relay WFS over an obviouscircuit and deenergizing relay EFS. The contacts of levers L2 and L6 areopen, to hold signals ZRAS, ZRBS, 6LAS and 6LBS at stop. I

At the western headblock location coders CT and 75CT are bothcontinually energized by an obvious circuit and each is operating itscontact at the corresponding code rates of 180 operations per minute and75 operations per minute, respectively. Signal control relay ZLAHR iscontrolled by a circuit which is not shown as it forms no part of myinvention. For the purposes of this description, it will suflice to saythat relay ZLAHR is energized unless signal 2LS displays its stop or redaspect. As shown, signal 2LS is at stop and relay 2LAHR is thereforedeenergized.

The polar stick relays 2DSR and ZDSKR are both in their normal orleft-hand position for reasons which will become clear as thisdescription progresses. With relay ZDSKR in its normal or left-handposition, reverse repeater relay 2DSKRPR will be released since itsenergizing circuit is open at reverse contact b of relay ZDSKR.Accordingly, energy will be supplied to the winding of code transmittingrelay ZWCTR at a 75 code rate over a circuit which may be traced frompositive terminal B of battery LB, over contact a of coder 75CT which isoperating at a code rate of 75 operations per minute, back contact a ofrelay ZLAHR, back contact a of relay ZDSKRPR, and the winding of relayZWCTR to negative terminal N of battery LB. Therefore, relay 2WCTR willbe operating its contact a at a 75 code rate.

With relay ZWCTR so operating, energy will be supplied to track section4T from track battery 4WTB at a 75 code rate over a circuit which maybe'traced from Feed-back code flows in the opposite directhe positive.terminal of track battery ,4WTB,over.the normal contact d of relayZDSKR, normal contactb of relay ZDRS, front contact a of relay ZWCTRwhich is operating at a 75 code rate, to the rail 1, and from the rail 2to the center tap of track battery 4WTB which is negative with respectto rail 1.

At the intermediate signal location IS, with code transmitting relay4ECTR released, current will flow from rail 1, over back contact a ofrelay 4ECTR, the windings of relays 4EVR and 4WTR in series, and back torail 2. With relays 4EVR and 4WTR connected in the manner shown in Fig.1B, relay 4WTR will pick up on each code impulse and relay 4EVR willremain continuously released.

When relay 4WTR operates its contacts, energy from battery LB will flowthrough the primary winding P of decoding transformer 4WTT over anobvious circuit governed by contact a of relay 4WTR. ,Due to transformeraction in transformer 4WTT, a voltage will be induced in secondarywindings S1 and S2 of transformer 4WTT. The resulting energy in windingS2 is mechanically rectified by contact b of relay 4WTR and supplied tothe winding of relay 4WHR, so that relay 4WHR will become energized andwill pick up. Relay 4WHR is sufficiently slow in releasing its contactsto cause it to remain picked up during the short intervals between codepulses during which no energy is supplied to its windingfrom thetransformer 4WTT.

When relay 4WHR picks up, the voltage induced in winding Slwill beapplied toprimary winding P of impulse transformer 4WWT over a circuitwhich includes front contact a of relay 4WHR. The voltage across thewinding P of transformer 4WWT will induce a voltage across the secondarywinding S of transformer 4WWT and current will flow through a circuitincluding normal contact 0 of relay 4DSR in multiple with front contactb of relay 4DSNPR, these contacts being closed for reasons which will bemade clear subsequently, the winding of relay 4ECTR and negativeterminal N of battery LB. The parts are proportioned and arranged andthe polarity is such that the energy supplied to the winding of relay'4ECTR is efiective to pick up the contacts of relay 4ECTR only upon therelease of the contacts of relay 4WTR. Accordingly, relay 4ECTR willpick up momentarily each time that relay 4WTR releases and therebyconnect trackbattery 4ETB to the rails 1 and 2 over a circuit which maybe traced from the positive terminal of track battery 4ETB, over frontcontact 12 of relay 4WVPR which is energized for reasons which will bemade clear presently, front contact a of relay 4ECTR to the rail 1, andfrom the rail 2 to the center tap of battery 4ETB which is negative withrespect to rail 1. The purpose of this reverse or feed-back energizationwill be made clear as the description proceeds.

From the foregoing it will be seen that, at this time, relay 4WHR willremain picked up and relay 4ECTR will operate at a code rate equal tothe code rate at which relay ZWCTR is operating, that is 75 operationsper minute, to supply feed-back code energy to section 4T.

The feed-back code energy which relay 4ECTR transmits to section 4T willbe received at the western headblock location during the off or releasedtime of relay ZWCTR. Accordingly, current will flow from rail 1, overback contact a of relay ZWCTR, and through the windings of relays ZWVRand 2ETR, in series, to the rail 2. Relays 2WVR and ZETR are soconnected that with current flowing through them in the manner justdescribed, relay ZWVR will operate and relay ZETR will remain released.It is apparent that each time a pulse is received, relay 2WVR will pickup and thereafter release and, therefore, operate at the same code rateas the code transmitting relay 4ECTR is located IS, that is, 75operations per minute.

With relay ZWVRso operating, current pulses .will be supplied frombattery LE to winding P of transformer 2WTT 75 times per minute overcontact a of relay ZWVR. By transformer action, a voltage will beinduced in winding S2 of transformer 2WTT each time a pulse of energy issupplied to Winding P of transformer ZWTT and this voltage ismechanicallyrectified by contact b ofrelay 2WVR thereby causing relayZWVPR to pick up and remain picked up as long as relay ZWVR continues tooperate. With relay 2ETR continuously deenergized, relay ZEHR will bedeenergized.

With relay ZWVPR picked up, the .upper winding of relay ZDSKR will beenergized so that its contacts will remain, or be operatedtotheir-normal position by a circuit which may be traced from positiveterminal B of battery LB, over front contact b of relay WFS, frontcontact b of relay ZWVPR, and the upper winding of relay ZDSKRtonegative terminal N of battery LB.

The energizing circuits for signal control relays ZRAHR and ZRBHR, whichwill be described in detail subsequently, are both open and relays ZRAHRand ZRBHR are both released. Thecontrol circuit for approach relay 2RARis not shown as it forms no part of my invention. Suffice it to say thatrelay ZRAR is energized unless an eastbound train is approaching signal2RAS. With the track stretch in approach to signal 2RAS unoccupied, aswill be assumed at this time, relay 2RAR isenergized. Therefore,approach locking relay ZRMSRis energized by a circuit which can betraced from the positive terminal B of battery LB, over back contact aof relay ZRAHR, back contact a of relay ZRBHR, front contacta of relayZRAR, and the winding of relay ZRMSR tonegative terminal N of batteryLB. Accordingly, the upper winding of relay 2DSR will be energized sothatits contacts will remain, or be operated to their normal position bya circuit which may be traced from the positive terminal B of batteryLB, over front contact b of relay ZRMSR, front contact a of relay WFS,front contact a of relay ZTR, normal contact a of relay ZDSKR, and theupper winding of relay 2DSR to negative terminal N of battery LB.

Assuming that switch 1W is in its normal position, as shown, so thattraflic will move directly along the main line and not out of or intothe passing siding including rails 3 and 4, the switch circuitcontroller associated with switch 1W will have its contact 10 open andcontact 11- closed. It will be seen that signal control relay ZRAHR whenenergized is energized over a circuit which may be traced from thepositive terminal B of battery LB, over the contact of lever L2,reversecontact c of relay ZDSKR, front contact b of relay 2TR, frontcontact 0 of relay ZEHR, contact 11, and the winding of relayZRAHR tothe negative terminal N of battery LB. It will further be seen thatsignal control relay ZRBHR, when energized, will be energized over acircuit which may be traced from positive terminal B of battery LB, overthe contact of lever L2, reverse contacts of relay ZDSKR, front contactb of relay 2TR, front contact 0 of relay ZEHR, contact 10 of the circuitcontroller associated with switch 1W, and the winding of relay ZRBHR tothe negative terminal N of battery LB. However, due to the fact thatrelay 2DSKR is in its normal position, relay ZEHR is released, and thecontact of lever L2 is open, neither of these signal control relays willbe picked up. With signal control relays both released, both signalsZRAS and ZRBS will display red aspects because o'fthe energization oftheir red lamps R by obvious circuits.

Considering now the apparatus at the intermediate signal location IS,for reasons which will 'be made clear presently, relay 4WVPR isenergized. With this condition existing, polar stick relay 4DSR will beenergized with its contacts in their normal-or left-hand position by acircuit which may be traced from the positive terminal -B of the batteryLB, over front contact a of relay 4WVPR, frontcontact b of relay 4WHR,and the upper winding of relay 4DSR to the'negative terminal N ofbattery 13B.

With relay 4DSR so energized, normal repeater relay 4DSNPR will beenergized by an obvious circuit including normal contact a of relay4DSR.

Coders 75CT and 180CT are energized in multiple by an obvious circuit sothat each of their front contacts a will be operating at a 75 code rateand 180 code rate, respectively. With relay 4WHR picked up, 180 codewill be supplied to code transmitting relay 4WCTR over a circuit whichmay be traced from the positive terminal B of battery LB, over frontcontact a of coder 180CT which is operating at 180 times per minute,front contact c of relay 4WHR, back contact a of relay 4DSRPR, normalcontact b of relay 4DSR, and the winding of relay 4WCTR to the negativeterminal N of battery LB. Accordingly, code transmitting relay 4WCTRwill operate its contact at a code rate of 180 pulses per minute. Withcode transmitting relay 4WCTR so operating, l80 code will be supplied tosection 6AT from track battery 6AWT B over a circuit which may be tracedfrom the positive terminal of battery 6AWTB, over front contact d ofrelay 4WHR and back contact b of relay 4EVPR in multiple, front contacta of relay 4WCTR, to the rail 1, and from rail 2 to the center tap ofbattery 6AWTB which is negative with respect to rail 1.

At the cut section location CS, Fig. 1C, as the coded energy from trackbattery 6AWTB is received, with relay CECTR released, current will flowfrom rail 1, over back contact a of relay CECTR, through the winding ofrelays CEVR and CWTR, in series, to rail 2, so that with relays CEVR andCWTR connected as shown, relay CWTR will operate its contacts and relayCEVR will remain continuously released. As relay CWTR operates, energywill be supplied from battery LB to the primary winding P of transformerAWTT, over contact a of relay CWT R and this energy will cause a voltageto be induced in secondary windings S1 and S2 of transformer AWTT. Withwinding S2 of transformer AWT T so energized, current will flow throughthe winding of relay CWHR over the rectifying contact b of relay CWTRcausing relay CWHR to pick up. With relay CWHR picked up, current willflow from the winding S1 of transformer AWTT through the Winding P ofimpulse transformer CWWT, thereby inducing a voltage in winding S oftransformer CWWT. With relay CDSR energized to its normal or left-handposition for reasons which will become clear presently, and relay CDSNPRpicked up by an obvious circuit, current will flow from the secondarywinding S of transformer CWWT, over front contact a of relay CDSNPR andnormal contact b of relay CDSR in multiple, and through the winding ofrelay CECTR to the negative terminal N and thence to the other terminalof winding S of transformer CWWT. The parts are proportioned andarranged and the polarity is such that, at this time, relay CECTR willbe picked up momentarily upon each release of the contacts of relayCWTR.

With relay CECTR so operating feed-back code energy will be transmittedto the rails 1 and 2 from track battery GAETB over a circuit which maybe traced from the positive terminal of battery 6AETB, over frontcontact b of relay CWVPR which is energized for reasons which will bemade clear hereafter, front contact a of relay CECTR which is operatingat a 180 code rate, to the rail 1, and from the rail 2 to the center tapof the track battery 6AETB which is negative with respect to rail 1.

Referring now to Fig. 1B, with relay 4WCTR released and rail 1 ofsection 6A1 positively energized and rail 2 energized negatively byfeed-back energy from location CS, current will flow from rail 1, overback contact a of relay 4WCTR and the windings of relays 4WVR and 4ETRto rail 2. With relays 4ETR and 4WVR connected in the manner shown inFig. 1B, relay 4WVR will operate at a 180 code rate and relay 4ETR willremain released. In the same manner as described for relays 4 WTR and4WHR, this codefollowing operation of 8 relay 4WVR will cause the codedetecting relay 4WVPR to be energized.

The circuits controlling the signals 4RS and 4LS will be described insome detail subsequently. For the present it will be pointed out thatnone of the lamps of signal 4RS is energized because the common returnfor all of the lamps of this signal to the negative terminal N ofbattery LB is open at back contact 1 of relay 4WHR and none of the lampsof signal 4LS is energized because the common return for all of thelamps of this signal to the negative terminal N of battery LB is open atback contact c of relay 4WVPR.

At the cut section location CS, Fig. 1C, code transmitting relay CWCTRwill be energized at a code rate by a circuit which may be traced frompositive terminal B of battery LB, over front contact 0 of relay CWTRwhich is operating at 21.180 code rate, back contact a of relay CDSRPR,normal contact c of relay CDSR, and the winding of relay CWCTR to thenegative terminal N of battery LB. With code transmitting relay CWCTR sooperating, energy will be supplied to section 6BT from track battery6BWTB at a 180 code rate over a circuit which may be traced from thepositive terminal of track battery 6BWTB, over front contact c of relayCWHR and back contact b of relay CEVPR in multiple,

and front contact a of relay CWCTR which is operatingat a 180 code rateto rail 1, and from rail 2 to the center tap of track battery 6BWTBwhich is negative with respect to rail 1.

With rail 1 energized with energy of positive polarity and rail .2 withenergy of negative polarity, in a manner similar to that alreadydescribed with relation to track section 4T, relay 6WTR, Fig. ID, willoperate at a 180 code rate and relay 6EVR will remain releasedcontinuously at this time. Accordingly, relay 6WHR will pick up and theprimary winding P of impulse transformer E6 will be energized 180 timesper minute. Code transmitting relay 6ECTR will operate at a 180 coderate over a circuit which may be traced from the lower terminal of thesecondary winding S of impulse transformer E6, over front contact a ofrelay 6DSKNPR which is energized in a manner to be described presentlyand the winding of relay 6ECTR to negative terminal N of battery LB andthe upper terminal of transformer E6. -With relay 6ECTR so operating,feed-back code energy will be supplied to the rails 1 and 2 from battery6BETB over a circuit which may be traced from the positive terminal oftrack battery 6BETB, over front contact 0 of relay 6LMSR which isenergized in a manner to be made clear subsequently, front contact d oftrack relay 8TR, normal contact b of relay 6DSR which is energized toits normal position by a circuit which will be traced presently, frontcontact a of relay 6ECTR which is operating at a 180 code rate to rail1, and from rail 2 to the center tap of battery 6BET B which is negativewith respect to rail 1.

When section 6BT is energized with feed-back code energy, relay CWCTR,Fig. 1C, will be released and current will flow from rail 1, over backcontact a of relay CWCTR, through the winding of relay CWVR, and thewinding of relay CETR to the rail 2. With relays CETR and CWVR connectedas shown in Fig. 1C, relay CWVR will operate and relay CETR will remaincontinuously released. Each time a feed-back pulse is transmitted tosection 6BT, relay CWVR will pick up so that it will operate at the coderate of relay 6ECTR, that is, 180 operations per minute.

The code following action of relay CWVR is detected in a manner similarto that previously explained for the other code following track relays,by action of the decoding transformer BWTT and relay CWVPR. Accordingly,relay CWVPR will be picked up at this time.

With relay CWVPR picked up, the upper winding of relay CDSR becomesenergized so that its contacts assume their normal or left-hand positionby a circuit which runs from the positive terminal B of battery LB, over9 front contact a of relay CWVPR, front contact b of relay CWHR, and theupper winding of relay CDSR .to the negative terminal N of battery LB.

.As was stated earlier, the DS and DSK relays herein employed are of thepolar stick type, that is, the contacts will remain in the position towhich they were last energized until energy of opposite polarity isapplied to the relay to move the contacts to their opposite position.Consequently, the contacts of relay 6DSR, Fig. 1D, will be found intheir normal position although at the present time neither winding isenergized. Relay 6DSKR will be energized to its normal or left-handposition over a circuit which may be traced from the positive terminal Bof battery LB, over back contact b of relay EFS, front contact b ofrelay 6WHR, normal contact \a of relay 6DSR, and the upper winding ofrelay 6DSKR to the negative terminal N of battery LB. At this time,normal repeater relay 6DSKNPR will be energized by an obvious circuitincluding normal contact b of relay 6DSKR.

Assuming switch 5W is in its normal position so that traffic will movedirectly along the main line and not into or out of the passing sidingincluding the rails 5 and 6, the switch circuit controller associatedwith switch 5W will have its contact 12 open and its contact '13 closed.It will be seen that signal control relay 6LAHR, when energized, isenergized over a circuit which may be traced from positive terminal B ofbattery LB, over the contact of lever L6, normal contact c of relay6DSKR, front contact b of relay 8TR, front contact a of relay 6WHR,contact 13 of the switch circuit controller, and the winding of relay6LAHR to negative terminal N of battery LB. It will be further seen thatthe signal control relay GLBHR, when energized, is energized over acircuit which may be traced from positive terminal B of battery LB, overthe contact of lever L6, normal contact c of relay 6DSKR, front contactb of relay 8TR, front contact c of relay 6WHR, switch circuit controllercontact 12, and the winding of realy GLBHR to negative terminal N ofbattery LB. However, due to the fact that lever L6 is in its normal oropen position, both energizingcircuits will be open at the contact oflever L6 and both signal control relays 6LAHR and -6LBHR will bereleased. With thesignal control relays both released, bothsignals 6LASand 6L BS will display red aspects due to the energization of their redlamps R by obvious circuits.

Decoding unit 180DU is connected to the terminals of winding P oftransformer 6WTT which is being energized at a 180 code rate.Accordingly, energy is supplied to the decoding unit at a code rate of180 and at this code rate sufiicient energy will be supplied to thewinding of relay 6DR to cause it to pick up. However, with relays 6LAHRand 6LBHR both released, the fact that relay 6DR is picked up will haveno effect upon the aspects displayed by signals 6LAS and 6LBS at thistime.

Having described the circuit arrangement in its normal condition, thatis, set up for trafiic moving in the normal westbound direction, it willnow be assumed that a train approaches the track stretch from the east.As the train approaches section 8T, signal ZLS, by means not shown, willbe cleared .to a green or clear aspect, and relay ZLAHR will pick up,transferring the control circuit for code transmitting relay ZWCTR fromthe 75 coder to the 180 coder. Accordingly, section 4T will becomeenergized with normal and feed-back codes of normal polarity at a 180code rate, so that relay 4DR, Fig. 1B, becomes picked up at this time.The remainder of the system will continue to operate as described above.Also, a leverman at the eastern headblock or the operator of thecentralized traffic control equipment will close lever L6, Fig. 1D. Withthe contact of lever L6 closed, relay 6LAHR will pick up because itspreviously traced energizing circuit will now be closed. Of course, ifthe train were to approach .on the eastern passing siding, includingrails 5 and 6, then switch SW would be thrown 10 by the. operator to.its reverse position and relay 6LBHR would pick up rather than relay6LAHR.

With relay 6LAHR picked up, the green lamp G of signal 6LAS will belighted due to energization by the circuit which may be traced frompositive terminal B of battery LB, over front contact b of relay 6LAHR,front contact a of relay 6DR, and the green lamp G to negative terminalN of battery 'LB. With relay 6LAHR picked up, relay 6LMSR will release.Upon the release of relay 6LMSR, the polarity .of the coded feed-backenergy being transmitted by code transmitting relay 6ECTR will bereversed .and the rails 1 and 2 will now be energized by a circuit whichmaybe traced from the negativeterminal of battery 6BETB, over backcontact 0 of relay 6LMSR, front contact a of relay 8TR, normal contact bof relay 6DSR, front contact a of relay 6ECTR which is operating at a180 code rate to the rail 1, and from the rail 2 to the center tap ofbattery 6BETB which is positive with respect to rail 1. At the cutsection CS, in a manner similar to that described for the feed-back codeof normal polarity, relay CETR will commence operating at a 180 coderate and relay CWVR will release and stay released. Accordingly relayCEHR will pick up and relay CWVPR will release. With relay CWV PR'nowreleased, the upper winding of relay CDSR will become deenergizedbut, because of the stick characteristic of the CDSR relay, the contactsof relay CDSR will remain in their normal position. Furthermore, withrelay CEHR now picked up and relay CWVPR released, the feed-back codetransmitted by code transmitting -relay CECTR will be of reversepolarity and will be transmitted-to the rails 1 and 2 of section 6AT bya circuit which may be traced from the negative terminal of trackbattery 6AETB, over back contact b of relay CW-VP-R and front contact 0of relay CEHR in multiple, front contact a of relay CECTR which isoperating at a 180 code rate to the rail 1, and from the rail 2 to thecenter tap of battery 6AETB which is positive with respect to rail 1.

With feed-back code being applied to track section 6AT with reversepolarity, in a manner similar to that described with respect to section6BT, relay 4ET R, Fig. 13, will commence operating at a 180 code rateand relay 4WVR will cease operating. Therefore, relay 4EHR will pick upand relay 4WVPR will release. Upon the release of relay 4WVPR, the upperwinding of relay 4DSR will become deenergized, but the contacts of relay4DSR will remain in their normal position due to the stickcharacteristic of the relay.

Upon the release of relay 4WVPR and the picking up of relay 4EHR, thefeed-back code being transmitted to section 4T by code transmittingrelay 4ECTR will be of opposite polarity to that transmitted when thecircuit is operating under normal conditions. The circuit which will nowsupply energy from battery 4ETB to the rails 1 and 2 in section 4T maybe traced from the negative terminal of battery .4ETB, over frontcontact d of relay 4EHR and back contact b of relay 4WVPR in multiple,front'contacta of zrelay'4ECTR which is now operating at a 180 code rateto the rail 1, and from the rail 2 to the center tap of battery 4ETBwhich is positive with respect to rail 1.

:With the feed-back code energy supplied to section 4T .being ofnegative polarity, relay ZETR, Fig. 1A, willcommence operating and relayZEHR will pick up, and [relays .2WVR and ZWVPR will release. This willcause the upper winding of relay ZDSKR to become deenergized but thecontacts of relay ZDSKR will remain in. their normal position due to thestick characteristic of .relay ZDSKR. This will prevent traffic fromentering the stretch from the western headblock in the reversedirection,for reasons which will become apparent as this description progresses.

-As the train enters section 8T, its wheels and axles shunt track relayw8TR causing it to release, thereby opening the energizing circuit forsignal control relay 6LAHR at contact b of relay 8TR, and causing thecontrol relay 6LAHR to release. Upon the release of the relay 6LAHR,signal 6LAS will display a red aspect due to the energization of the redlamp R of signal 6LAS by a circuit which may be traced from the positiveterminal B of battery LB, over back contact b of relay 6LAHR and the redlamp R to the negative terminal N of battery LB.

The release of relays 6LAHR and 8TR also establishes a circuit,including back contact a of relay 6LAHR and back contact c of relay 8TR,for reenergizing approach locking relay GLMSR, which then sticks overback contacts a of the signal control relays. However, feed-back codebeing transmitted from the eastern headblock location will continue tobe of reverse polarity since, with relay 8TR released, rails 1 and 2will be energized by a circuit which may be traced from the negativeterminal of battery 6BETB, over back contact d of relay 8TR, normalcontact b of relay 6DSR, front contact a of relay GECTR operating at a180 code rate, to the rail 1, and from the rail 2 to the center tap ofbattery 6BETB which is positive with respect to rail 1. Accordingly, allof the feed-back energy being transmitted to the stretch will be ofreverse polarity.

Upon the train entering section 6BT but having not yet vacated section8T, the wheels and axles of the train will shunt relays 6EVR and 6WTRcausing them to remain released. Accordingly, relay 6WHR will alsorelease because it is now receiving no energy from the winding S2 oftransformer 6WTT. Upon the release of relay 6WHR, the energizing circuitfor signal control relay 6LAHR will become open at front contact ofrelay 6WHR as well as front contact b of track relay 8TR. The release ofrelay 6WHR will also open the energizing circuit for the upper windingof relay 6DSKR at front contact b of relay 6WHR. However, due to thestick characteristic of relay GDSKR, its contacts will remain in theirnormal or left-hand position.

Upon the release of relays 6WTR and 6WHR, no code impulses will besupplied to winding P of transformer E6 and, therefore, no energy willbe supplied to code transmitting relay 6ECTR and it will cease tooperate. Accordingly, because of the train shunt and also because of thecut-off of the feed-back code, no feed-back code will be received at thecut section location CS and relay CETR and its associated code detectingrelay CEHR will both release. However, although front contact 0 of relayCEHR is now open, back contact b of relay CWVPR will be closed andfeed-back code of negative polarity will continue to be supplied tosection 6AT. In a similar manner to that already described, feedback ofnegative polarity will be supplied to all the other sections in thestretch and traffic will remain locked in the westbound direction.

Upon the train vacating section 8T, relay 8TR will pick up. This has noimmediate effect upon the circuit arrangement but as this descriptionproceeds it will become clear why the picking up of relay 8TR is useful.

Upon the train vacating section 6BT and occupying section 6AT, relayCWTR will become released due to the fact that it is shunted by thewheels and axles of the train. Therefore, no coded energy will besupplied from battery LB to code transmitting relay CWCTR and as aresult relays 6WTR and 6WHR at the eastern headblock will remainreleased. Therefore, no feed-back energy will be supplied from battery6BETB to section 6BT and relays CWVR, CETR, CEHR and CWVPR will remainreleased. With relay 6WHR remaining reno feed-back code will betransmitted by relay CECTR to section 6AT.

Upon the release of relay 4ETR, due to the train shunt in section 6AT,relay 4EHR will also release, opening its front contact d. However,because back contact b of relay 4WVPR is still closed, feed-back energyof reverse polarity will continue to be transmitted by relay 4ECTR tosection 4T in a manner already described. Upon the release of relay4EHR, energy will be supplied to the green lamp G of signal 4LS over acircuit which may be traced from the positive terminal B of battery LB,over normal contact d of relay 4DSR, front contact e of relay 4WHR,front contact a of relay 4DR, the green lamp G of signal 4LS, backcontact 1 of relay 4EHR, and back contact c of relay 4WVPR to negativeterminal N of battery LB. It should be noted that until the trainentered section 6AT, signal 4LS was not illuminated because the lightingcircuit was open, initially at the back contact 0 of relay 4WVPR andlater, after the change in polarity of the feed-back code, at backcontact 1 of relay 4EHR. This approach lighting feature is particularlydesirable whenever battery conservation is important. However, myinvention is not limited to the use of approach lighting and myapparatus will operate just as well where continuous lighting of thewayside signals is employed.

Clear control relay 4DR was previously described as supplied with energyfrom decoding unit DU which is of conventional design and well-known inthe art of coded railway signaling. Each decoding unit 180DU will supplysuflicient energy to its clear control relay when and only when thedecoding unit is energized at a 180 code rate. The decoding unitsupplying energy to relay 4DR will be energized at a 180 code rate andtherefore will be able to supply sufiicient energy to keep relay 4DRpicked up. The circuit which energizes the decoding unit may be tracedfrom the upper terminal of winding P of transformer 4WTT over backcontact 0 of relay 4DSRPR, the decoding unit 180DU, front contact 0 ofrelay 4DSNPR and to the lower terminal of winding P of transformer 4WTT.The coded feedback energy being transmitted by relay 4ECTR continues tobe of reverse polarity as the rails 1 and 2 in section 4T continue to beenergized by battery 4ETB over a circuit which has already been traced.

When the train vacates section 6AT and occupies section 4T, its wheelsand axles will shunt relays 4WTR and ZETR causing them to release andthereby causing relays 4WHR and ZEHR to release. Accordingly, no energyimpulses will be supplied to winding P of transformer 4WWT and,therefore, code transmitting relay 4ECTR will cease to transmitfeed-back energy to section 4T. Red lamp R of signal 4L3 will now beenergized by a circuit which may be traced from positive terminal B ofbattery LB, over normal contact d of relay 4DSR, back contact e of relay4WHR, the red lamp R of signal 4L5, back contact 1 of relay 4EHR, andback contact 0 of relay 4WHR to negative terminal N of battery LB.

With relay 4WHR nowv released, energy at a 75 code rate will be suppliedfrom battery LB to code transmitting relay 4WCTR over a circuit whichmay be traced from positive terminal B of battery LB, over front contacta of coder 75CT which is operating at a 75 code rate, back contact c ofrelay 4WHR, back contact a of relay 4DSRPR, normal contact b of relay4DSR, and the winding of relay 4WCTR to negative terminal N of batteryLB. Code transmitting relay 4WCTR will therefore transmit 75 code energyfrom battery GAWTB to the rails 1 and 2 of section 6AT of normalpolarity over a circuit which may be traced from the positive terminalof battery 6AWTB, over back contact b of relay 4EVPR, front contact a-ofrelay 4WCTR which is operating at a 75 code rate to the rail 1, and fromthe rail 2 to the center tap of battery 6AW'FB which is negative withrespect to rail 1. At the cut section location, operation of relay CWTRat a 75 code rate will occur, and accordingly the winding P oftransformer AWTI will be supplied with energy at a 75 code rate andenergy from winding S1 of transformer AWTI will be supplied to winding Pof transformer CWWI at the same code rate. In this manner energy will besupplied from winding S of transfonmer OWWT to code transmitting relayCECTR which will transmit feed-back code to the intermediate signallocation IS. The first few pulses of this feed-back code will be ofreverse polarity due to the fact that relay OWVPR is initially in adeenergized condition. Current thus flows from the negative terminal ofbattery 6AETB over back contact b of relay CWVP-R and front contact a ofrelay CECTR to rail 1, and from rail 2 to the center tap of the battery,which is positive with respect to rail 1. However, the feed-back codeshortly changes to normal polarity when relay CWVPR picks up, in themanner described shortly, permitting the current to flow from thepositive terminal of battery 6AETB, over front contact b of relay OWVPR,front contact a of relay CECTR, operating at a 75 code rate, to the rail1, and from the rail 2 to the center tap of battery '6ATB which isnegative with respect to rail 1.

With relay CWTR operating at a 75 code rate, energy will be supplied tocode transmitting relay CWCTR at the same code rate over a circuit whichhas already been traced. In a manner substantially similar to thatdescribed with relation to the circuits in their normal condition, relay6WTR will commence operating at a 75 code rate and relay 6WHR Will pickup. Furthermore, relay 6ECTR will transmit feed-back energy of normalpolarity to the cut section location which will cause relay CWVR tocommence operating and relay OWVPR to pick up. With transformer 6WTT nowbeing supplied with energy at a 75 code rate, code detecting unit 180DUwill not supply sufficient energy to pick up clear control relay -6DRand it will therefore remain released. Accordingly, signal 6LA-S, ifrecleared for a following train at this time, can only display a yellowaspect, the yellow lamp Y being energized by a circuit which may betraced from position terminal B of battery LB, over from contact b ofrelay 6LAHR, back contact a of relay 6'DR, the yellow lamp Y of signalGLAS to negative terminal N of battery LB. At this time, the circuitpreviously traced for the red lamp of signal 4LS is interrupted, eitherat back contact f of relay 4'EHR or at back contact c of relay 4WVPR,and the signal becomes dark.

When the train vacates section 4T and occupies section 2T, assuming thatsignal 6LAS was not recleared (lever L6 in-open position), relay ZLAHRwill release due to thefact that signal 'ZLS, which is controlled bycircuits which are not shown, will now display red. Energy at the 75code rate will be supplied to the Winding of relay 2WCTR by a circuitwhich may be traced from positive terminal B 'of battery LB, :overcontact a of 75CT which is operating at a 75 code rate, back contact aof relay ZLAHR, back contact-a of relay ZDSKRPR, and the winding ofrelay 2WCTR to 'negativeterniinal N of battery LB. Accordingly, relayZWCTR will transmit 75 code 'to section 4T by a circuit which maybetraced from the positive terminal -of battery 4WTB, over normal contactd of relay ZDSKR, normal contact 11 of relay .ZDSR, front contact a ofrelay 2WCTR which is operating at a '15 code rate to the rail 1, andfrom the rail 2 to center tap of'battery 4WTB which :is negative withrespect to rail 1. in a'manner similar to that already described withrespect to the normal condition of the circuit arrangement, codedfeed-back energy of normal polarity will 'be transmitted by transmittingrelay-4ECTR to section 4Ttat a 75 code rate thereby'operating relay'ZWVR and picking up relay ZWVPR. With relay 4WTR operating and relay4WI-IRpicked up, 180 code of normal polarity will be transmitted tosection 6AT and repeated to section 6BT. Feed-back code of normalpolarity but at the code rate will be transmitted by code transmittingrelay CECTR to section 6AT, with relay 4WVR operating to hold relay4WVPR energized. In like manner, normal code and feed-back code, both ofnormal polarity and of the 180 code rate, will be transmitted by relayCWCTR and relay GECTR, respectively, operating relays 6WTR and CWVR andholding up relays 6WHR and CWV PR.

With the system restored to its normal condition and both normal codeand feed-back code being of normal polarity, the direction of trafficmay now be reversed by throwing lever L1 to its eastbound position E.This will open the energizing circuit for relay WFS causing it torelease and will pick up relay EFS over an obvious circuit including theeastbound contact E of lever L1. Upon relay WFS releasing, the contactsof relay ZDSR will be operated to their reverse or right-hand positiondue to the lower winding of relay ZDSR becoming energized by a circuitwhich may be traced from positive terminal B of battery LB, over frontcontact b of relay ZRMSR, back contact a of relay WFS, front contact aof relay ZWVPR, and the lower winding of relay ZDSR to' negativeterminal N of battery LB. With the contacts of relay 2DSR in theirreverse position and code transmitting relay ZWCTR operating at a 75code rate, 75 code of reverse polarity will be transmitted to section 4Tover a circuit which may be traced from the negative terminal of battery4WTB, over front contact 0 of relay ZRMSR, front contact d of relay ZTR,reverse contact b of relay ZD-SR, front contact a of relay ZWCTR whichis operating at a 75 code rate, to the rail 1 and from the rail 2 to thecenter tap of battery 4WTB which is positive with respect to rail 1.

With the normal code on section 4T being of reverse polarity, relay 4EVRwill operate and relay 4WTR will remain released. Accordingly, relay4EVPR will pick up and relay 4WHR will release. This will result in thecode transmitted to section 6AT over front contact a of relay 4WCTRbeing of reverse polarity due to energization of the rails by a-circuitwhich may be traced from the negative terminal of battery 6AWTB, overfront contact b of relay 4EVPR, front contact a of relay 4WCTR operatingat a 75 code rate to the rail 1, and from the rail 2 to the center tapof battery 6AWTB which is positive with respect to rail 1. It is to benoted that, with relay 4WHR released, relay 4WCTR is now operating atthe 75 code rate, as controlled over a previously traced circuitincluding contact a of 75CT and back contact 0 of relay 4WHR.

Accordingly, at the cut section, relay CEVR will commence operating,relay CEVPR will pick up, relay CWTR will cease operating and relay CWHRwill release. Upon this happening, code of reverse polarity will besupplied to section 6BT from battery 6BWTB by a circuit which may betraced from the negative terminal of battery 6BWTB, over front contact bof relay CEVPR, front contact a of relay CWCTR which is operating at a75 code rate to the rail 1, and from the rail 2 to the center tap ofbattery 6BWTB which is positive with respect to rail 1.

The winding of code transmitting relay CWCTR will no longer be suppliedwith coded energy over front contact b of relay CWTR because this latterrelay is no longer operating. However, front contact c of relay CEVR isconnected in multiple with front contact 0 of relay CWTR. Therefore,coded energy is supplied through the winding of relay CWCTR over acircuit which may be traced from positive terminal B of battery LB, overfront contact 0 of relay CEVR which is operating at a code rate of 75times per minute, back contact a of relay CDSRPR, normal contact c ofrelay CDSR, and the winding of relay CWCTR to negative terminal Nofbattery LB.

Accordingly, at the eastern headblock, relay '6EVR 15 will commenceoperating and relay 6WTR will cease to operate. With relay 6EVR nowoperating, relay 6EVPR will pick up and with relay 6WTR now notoperating, relay 6WHR will release. Therefore, the contacts of relay6DSKR will be operated to their reverse position due to energization ofthe lower winding of relay 6DSKR by a circuit which may be traced frompositive terminal B of battery LB, over front contact b of relay EFS,front contact b of relay 6EVPR, and the lower winding of relay 6DSKR tonegative terminal N of battery LB. Upon relay 6DSKR operating to itsreverse position, a circuit will be established to energize the lowerwinding of relay 6DSR and it too will operate its contacts to theirreverse position. This circuit may be traced from positive terminal B ofbattery LB, over front contact b of relay 6LMSR, front contact a ofrelay EFS, front contact a of relay STR, reverse contact a of relay6DSKR, and the lower Winding of relay 6DSR to negative terminal N ofbattery LB.

When relay GDSKR operates to the reverse position,

the energizing circuit for relay 6DSKNPR will be opened at the normalcontact b of relay 6DSKR. However, relay GDSKNPR will not immediatelyrelease because of its slow release characteristic, and as long as relayGDSKNPR remains picked up, impulse transformer E6 will continue tosupply energy, now at the 75 code rate, to the winding of codetransmitting relay 6ECTR over a circuit which may be traced from thelower terminal of winding S of transformer E6, over front contact a ofrelay SDSKNPR, and the winding of relay 6ECTR to negative terminal N ofbattery LB which is also connected to the upper terminal of the windingS of transformer E6. The primary winding of transformer E6 is nowenergized from winding S1 of transformer 6ETT over back contact a ofrelay 6WHR. However, the feed-back code being transmitted by relay 6ECTRwill be of reverse polarity as can be seen from tracing the energizingcircuit for the rails 1 and 2 of track section 6BT from the negativeterminal of battery 6BETB, over reverse contact d of relay 6DSKR,reverse contact b of relay 6DSR, front contact a of relay 6ECTR which isoperating at a 75 code rate to the rail 1, and from the rail 2 to thecenter tap of battery 6BETB which is positive with respect to rail 1.

Accordingly, at the cut section location CS, relay CETR will commenceoperating, relay CWVR will cease operating, relay CEHR will pick up andrelay CWVPR will release. Upon this occurring the lower winding of relayCDSR will become energized over a circuit which may be traced from thepositive terminal B of battery LB, over front contact a of relay CEVPR,front contact b of relay CEHR, and the lower winding of relay CDSR tothe negative terminal N of battery LB. Therefore, relay CDSR willoperate to its reverse position and in so doing will deenergize slowrelease relay CDSNPR and energize relay CDSRPR over an obvious circuitincluding the reverse contact a of relay CDSR.

Upon relay CDSR operating to its reverse position and relay CDSRPRpicking up, the circuit which was supplying energy to relay CWCTR isinterrupted. This circuit, including contact of relay CEVR operating ata 75 code rate, will become open at contact a of relay CDSRPR and normalcontact 0 of relay CDSR. Relay CWCTR releases, opening its front contacta to interrupt the circuit supplying coded energy of reverse polarityfrom battery 6BWTB to the rails of section 6BT. Accordingly, relays 6EVRand 6EVPR will both release, thereby deenergizing the lower winding ofrelay 6DSKR. However, this will have no effect as to the position of thecontacts of relay GDSKR at the eastern headblock location because ofthat relays stick characteristic.

As long as relay CDSNPR remains picked up, transformer CWWT willcontinue to energize code transmitting relay CECTR which will continueto send out feedback code to section GAT. However, this code will now beof reverse polarity because the rails 1 and 2 of section 6AT will beenergized by a circuit which may be traced from the negative terminal ofbattery 6AETB, over front contact 0 of relay CEHR and back contact b ofrelay CWVPR in multiple, front contact a of relay CECTR which isoperating at a 75 code rate to the rail 1, and from the rail 2 to thecenter tap of battery 6AETB which is positive with respect to rail 1.

Therefore, at the intermediate signal location IS, relay 4ETR willcommence operating and relay 4WVR will release resulting in relay 4EHRpicking up and relay 4WVPR releasing. Accordingly, the lower winding ofrelay 4DSR will become energized by a circuit which may be traced frompositive terminal B of the battery LB, over front contact a of relay4EVPR, front contact b of relay 4EHR, and the lower winding of relay4DSR to negative terminal N of the battery LB. With the lower winding ofrelay 4DSR so energized the contacts of relay 4DSR will operate to theirreverse position and thereby deenergize relay 4DSNPR and energize relay4DSRPR. Relay 4DSNPR is a slow release relay and as long as it remainspicked up, winding S of transformer 4WWT will supply energy to codetransmitting relay 4ECTR which will thereby transmit feed-back code tosection 4T. The circuit supplying energy from the secondary winding S oftransformer 4WWT to relay 4ECTR may be traced from the right-handterminal of winding S, over front contact b of relay 4DSNPR, and thewinding of .relay 4ECTR to the negative terminal N of battery LB whichis also connected to the other terminal of winding S of transformer4WWT. However, this feed-back code being transmitted by relay 4ECTR willbe of reverse polarity and will be supplied from battery 4ETB to section4T over a circuit which may be traced from the negative terminal ofbattery 4ETB over front contact d of relay 4EHR and back contact b ofrelay 4WVPR in multiple, front contact a of relay 4ECTR which isoperating at a 75 code rate to the rail 1, and from the rail 2 to thecenter tap of battery 4ETB which is positive with respect to rail 1.

With the feed-back code transmitted by relay 4ECTR being of negativepolarity, relay ZETR will commence operating and relay ZWVR will ceaseoperating. Therefore, relay ZEHR will pick up and relay ZWVPR willrelease. The lower winding of relay ZDSKR will not become energized by acircuit which may be traced from positive terminal B of battery LB, overback contact b of relay WFS, front contact b of relay ZEHR, reversecontact a of relay ZDSR, and the lower winding of relay ZDSKR tonegative terminal N of battery LB. Upon relay ZDSKR operating itscontacts to their reverse position, relay ZDSKRPR will become energizedand open its back contact a to interrupt the circuit supplying energy torelay ZWCTR over contacts of the coders CT and 75CT. The closing offront contact a of relay ZDSKRPR completes a circuit for supplyingenergy from transformer W2 to relay ZWCTR, which will shortly supplyfeed-back code to track section 4T.

At the eastern headblock location relay 6DSKNPR eventually releases andcloses a circuit, at its back contact a connecting one of the coders,75CT or 180CT, depending upon traffic conditions, into the circuitarrangement to control the supply of energy to relay 6ECTR. With thestretch of track vacated as it is at this time, and relay GRAHRdeenergized, coder 750T will supply energy to code transmitting relay6ECTR over a circuit which may be traced from positive terminal B ofbattery LB, over the contact of 75CT which is operating at a 75 coderate, back contact a of relay 6RAHR, back contact a of relay 6DSKNPR,now released, and the winding of relay 6ECTR to negative terminal N ofbattery LB. Relay 6ECTR will now control normal code supplied frombattery 6BETB to the track section 6BT, which code will be of reversepolarity, the rails being energized by a circuit which has already beentraced in connection with feed-back code of reverse polarity previouslytransmitted by relay 6ECTR.

Accordingly, at the cut section location CS, relay CETR will remainoperating and relay CEHR will remain picked up, and relays CWVR andCWVPR will remain released. Relay CDSNPR which became dc.- energized butremained picked up due to its slow release characteristic eventuallyreleases. Energy Will besupplied to the winding P of impulse transformerCEWT by winding S1 of transformer BETT in a manner similar to thatdescribed with respect to other impulse transformers. The secondarywinding S of transformer CEWT will supply energy to code transmittingrelay CWCTR over a circuit which may be traced from the left-handterminal of winding S of transformer CEWT, over front contact b of relayCDSRPR, and the winding of relay CWCTR to the negative terminal N ofbattery LB which is connected also to the right-hand terminal of windingS of transformer CEWT. The feedback code being transmitted by relayCWCTR will be of the same frequency as the code being transmitted fromthe eastern headblock location, that is, 75 impulses per minute. Thisfeed-back code will be of reverse polarity which is supplied frombattery GBWTB to section 6BT by a circuit which may be traced from thenegative terminal of battery 6BWTB, over front contact b of relay CEVPR,front contact a of relay CWCTR which is operating at 75 code rate to therail 1, and from the rail 2 to the center tap of battery 6BWTB whichwill be positive with respect to rail 1. This feed-back code of reversepolarity will cause relay 6EVR to commence operating and relay 6EVPR topick up thereby reestablishing the energizing circuit for the lowerwinding of relay GDSKR.

Furthermore, at the cut section location CS, with relay CETR operatingat a 75 code rate, energy will be supplied from battery LB to codetransmitting relay CECTR at the same code rate over a circuit which maybe traced from positive terminal B of battery LB, over front contact ofrelay CETR operating at a 75 code rate, back contact b of relay CDSNPR,reverse contact b of relay CDSR, and the winding of relay CECTR tonegative terminal N of battery LB. Accordingly, energy of reversepolarity will be supplied, to section 6AT from the battery 6AETB by acircuit which may be traced from the negative terminal of battery 6AETB,over front contact c of relay CEHR and back contact b of relay CWVPR inmultiple, front contact a of relay CECTR which is operating at a 75 coderate to the rail 1, and from the rail 2 to the center tap of battery6AETB which is positive with respect to rail 1.

At the intermediate signal location IS, the code being transmitted bythe code transmitting relay CECTR will keep relay 4ETR operating whichin turn will cause relay 4EHR to remain picked up and relay 4WVR andrelay 4WVPR to remain released. With the contacts of relay 4DSR nowoperated to their reverse positions, impulse transformer 4EWT willsupply coded energy to the wind ing of relay 4WCTR over a circuit whichmay be traced from the left-hand terminal of the winding S oftransformer 4EWT, over front contact b of relay 4DSRPR and reversecontact b of relay 4DSR in multiple, and the winding of relay 4WCTR tothe negative terminal N of battery LB which is also connected to theright-hand terminal of the winding 8 of transformer 4EWT. The primarywinding P of transformer 4EWT will be supplied with energy from thewinding S1 of transformer 6AETT in a manner similar to that alreadydescribed with respect to the energization of other impulsetransformers. However, the feed-back code being transmitted by relay4WCTR will be of reverse polarity because the rails of section 6AT willbe energized from battery 6AWTB over a circuit which has already beentraced with respect to supplying normal code to the section 6AT.Accordingly, at the cut section location CS relay CEVR will remainoperating and relay CEVPR will remain picked up and relays CWTR and CWHRwill remain released.

At the intermediate signal location, coder 1811GT will code energysupplied from the battery LB to code transmitting relay 4ECTR by acircuit which may be traced from the positive terminal B of the batteryLB over the front contact a of coder ISGCT which is operating at a coderate, front contact 0 of relay 4EHR, back contact a of relay 4DSNPR,reverse contact 0 of relay 4DSR, and the winding of relay 4ECTR to thenegative terminal N of battery LB. Accordingly, relay 4ECTR will operateat a 180 code rate and will code the energy supplied to the section 4T,which will be of reverse polarity, over a circuit which was alreadydescribed with relation to the supply of feed-back code of reversepolarity from battery 4ETB to the section 4T.

With track section 4T being energized with energy of reverse polarity,relay 2ETR will continue operating and relay 2EHR will remain picked up,and relays ZWVR and ZWVPR will remain released. Relay ZDSKRPR hasalready picked up and, accordingly, transformer W2 will be operating asan impulse transformer and supplying energy to relay 'ZWCTR over acircuit which may be traced from the lower terminal of winding S oftransformer W2, over front contact a of relay ZDSKRPR, and the Windingof relay ZWCTR to the negative terminal N of battery LB which is alsoconnected to the upper terminal of the winding S of transformer W2.Winding S1 of decoding transformer ZETT will supply energy to theprimary winding of transformer W2 in a manner-already described.Therefore, feed-back code will be supplied to the track section 4T fromthe battery 4WTB and this code will be of reverse polarity due to thefact that the track section 4T will be energized over a circuit whichhas already been traced with relation to normal code of reverse polaritybeing transmitted by relay ZWCTR. Therefore, at the intermediate signallocation IS, relay 4EVR will commence operating on feed-back code andrelay 4EVPR will remain picked up, and relays 4WTR and 4WHR will remainreleased. The circuit arrangement as now described is ready for amovement of a train in the direction opposite to the normal direction,that is, for an eastbound train movement.

It should be noted at this time that with the apparatus set for awestbound train movement, had any of these track sections been occupiedso that the feed-back code in any of the track sections was of reversepolarity at the time lever L1 was thrown to its reverse position, itwould have been impossible for the polar relays in the several tracksections of the track stretch to have cascaded to their reversepositions so that traffic could be cleared for the eastbound trafficmovement. It is because of this necessity for the circuit arrangement tobe sending out normal andfeed-back code of normal polarity in order toreverse trafiic from westbound to eastbound that a complete locking ofthe traflic direction in one direction is achieved once a train hasentered the stretch.

With the circuit arrangement now set for an eastbound train movement,let it be assumed that a train on the main track approaches section 2Tfrom the west. Signal control lever L2 will be closed, energizing signalcontrol relay 2RAHR, so that signal 2RAS displays a green aspect sincerelay 2ETR is operating at 180 code rate and relay ZDR is energized.When relay 2RAHR picks up, relay ZRMSR will release. Accordingly, thepolarity of the feed-back code being transmitted by relay ZWCTR will bechanged by contact 0 of relay ZRMSR, that is, the feed-back code willnow be of normal polarity rather than of reverse polarity. In a mannersimilar to that described with respect to a westbound movement, thisfeed-back code of normal polarity will cascade from the Westernheadblockto the eastern headblock so that all the feed-back codetransmitted on the track stretch will be of normal polarity whereas, thenormal code will continue to be of reverse polarity. This will releaserelay eEVPR at the eastern headblockand will prevent any operation ofthe traflic relay 6DSR, so that the direction of trafiic cannot bechanged. Relay 6WTR at the eastern headblock location will commence tooperate and will pick up relay 6WHR and, when signal GRS is cleared,relay oDR. The picking up of these relays, however, will have no effectbecause all signal control circuits controlled by these relays are alsocontrolled by either relay 6DSR or relay 6DSKR in their normal position.Since these latter two relays are in their reverse positions, there isno change in the signal controls, and it will be impossible to clearsignals 6LBS or 6LAS at this time.

When a train occupies section 2T, the wheels and axles of the train willshunt relay ZTR causing it to release and thereby opening the energizingcircuit for signal control relay ZRAHR causing it to release. Therefore,the red lamp R of signal ZRAS will he lighted and signal ZRAS willindicate stop. The circuit energizing the red lamp may be traced frompositive terminal B of battery LB, over back contact 12 of signalcontrol relay ZRAHR and the red lamp R of signal ZRAS to negativeterminal N of battery LB. With relay 2TR released, the feedback codebeing transmitted by code transmitting relay ZWCTR will continue to beof normal polarity even though approach locking relay 2RMSR is nowpicked up. Accordingly, feed-back code being transmitted all along thetrack stretch will be of normal polarity. When the train occupiessection 4T the wheels and axles of the train will shunt the normal codebeing transmitted by relay ECTR and relays ZETR and 2WVR will bothbecome released. Therefore, no feedback code will be transmitted tosection 4T. With relay ZETR released, relay ZEHR will release, therebyadditionally opening the energizing circuit for relay ZRAHR.Accordingly, signal ZRAS will continue to display a red aspect.

At the intermediate signal location IS, relays 4EVR, 4WTR, 4EVPR and4WHR will all be released. Signal 4R8 will display a green aspect,assuming that signal 6R5 is now cleared, due to the energization of thegreen lamp G by a circuit which may be traced from the positive terminalB of battery LB, over reverse contact d of relay 4DSR, front contact eof relay 4EHR, front contact b of relay 4DR, which is energized whensignal 6R5 is cleared, green lamp G of signal 4R5, back contact f ofrelay lWHR, and back contact c of relay 4EVPR to the negative terminal Nof battery LB. However, the lamps of signal 4L5 will be deenergized dueto the fact that relay 4EHR is picked up thereby opening the energizingcircuit for signal 4L5 at back contact 1 of relay 4EHR.

When the train occupies section (rAT, any energy transmitted to thattrack section will be shunted by the wheels and axles of the trainthereby causing relays 4ETR, 4WVR, 4-EHR and 4WVPR to release.Accordingly, relay 4lECTR will commence to operate at a 75 code rate dueto its energization by a circuit which may be traced from positiveterminal B of battery LB, over the contact a of coder '75CT which isoperating at a 75 code rate, back contact 0 of relay lEI-IR, backcontact a of relay lDSNPR, reverse contact 0 of relay 4DSR, and thewinding of relay 4ECTR to negative terminal N of battery LB.Accordingly, at the western headblock location, relay ZETR and relayZEHR will pick up and relay ZWCTR will commence transmitting feed-backcode of reverse polarity. Due to the fact that normal and feed-back codeon section 4T will be coded at a rate of 75 pulses per minute, clearcontrol relay 2BR will remain released. Accordingly, if signal ERAS isrecleared for a following train, it can only display a yellow aspect,since contact a of relay ZDR is released. Signal 4R8 will now be in acondition to display a red aspect, if a train were to enter section 4T,due to the completion of the circuit which may be traced from positiveterminal B of battery LB, over reverse contact d of relay ADSR, backcontact e of relay 4EHR, the red lamp R of the signal 4R3, back 20contact 1 of relay 4WHR, and back contact 0 of relay 4EVPR to negativeterminal N of battery LB. However, with no train in section 4T, relay4EVPR is picked up and signal 4R8 will be dark, its energizing circuitbeing opened at back contact 0 of relay 4EVPR.

With no feed-back code being received over section 6AT, relays CEVR,CWTR, CEVPR and CWHR will all be released. Accordingly, the feed-backcode transmitted by code transmitting relay CWCTR will be of normalpolarity which, as already has been explained, is opposite to the usualpolarity established for an eastbound train movement. The feed-back codewill be of normal polarity due to the fact that the rails or" section613T will be energized by a circuit which may be traced from thepositive terminal of battery 6BWTB, over back contact 12 of relay CEVPR,front contact a of relay CWCTR which is now operating at a code rate, tothe rail 1, and from the rail 2 to the center tap of battery 6BWTB whichis negative with respect to rail 1.

Accordingly, relay 6WTR will continue to operate and relay 6WHR willremain energized, and relays EVR and 6EVPR will remain released. RelayCECTR will be operating at a 180 code rate transmitting normal code ofreverse polarity to track section 6AT. However, with the train occupyingsection 6AT, relays 4ETR, 4WVR, 4EHR and 4WVPR will all be released aspreviously noted, as well as relays CEVR, CW'lR, CEVPR and CWHR. Withthese relays released, the lower windings of relays 4DSR and CDSR willbe deenergized but these relays will remain in their reverse positiondue to their stick characteristics. Code transmitting relay 4ECTR willcontinue to transmit normal code at a 75 code rate to section 4T.

When the train occupies section 613T, any energy being supplied to thatsection will be shunted by the wheels and axles of the train therebycausing relays CETR, CEHR, 6WTR and 6WHR to release. Furthermore, relaysCWVR, CWVPR, 6EVR and GEVPR are already released. Accordingly, relayCECTR will not be supplied with energy and it will release. Therefore,no normal code will be supplied to section AT from battery AETB, thuscausing relays 4ETR and Wt V R to remain released. With relays 4ETR and4WVR both released, no energy will be supplied to relay 4WCTR and,therefore, no feedback code will be supplied to section 6AT.Accordingly, relays CEVR and CWTR will be released. I

Section 4T will be supplied with normal and feed-back codes of reversepolarity in a manner substantially the same as that described when theeastbound train occupies section 6AT. Accordingly, in a manner alreadydescribed, signal 4RS will be in a condition to display its red aspect,but it will be dark, and signal ZRAS will be in a condition to displayits yellow aspect it the signal is cleared for a following move.

At the eastern headblock location, signals 6LAS and 6LBS will continueto display a red aspect for reasons made clear when the traificdirection reversal was described.

When the train occupies section 8T, relay 8TR will be shunted by thewheels and axles of the train and will, therefore, release. Theenergizing circuit for the lower winding of relay 6DSR will become openat front contact a of relay 8TR but relay 6DSR will remain in itsreverse position due to its stick characteristic. Signal 6R8, which iscontrolled by means not shown, will display a stop or red aspect and,therefore, relay 6RAHR will be released. Accordingly, 75 code will besupplied to relay 6ECTR by a circuit which may be traced from positiveterminal B of battery LB, over the front contact of coder 75CT which isoperating at a 75 code rate, back contact a of relay 6RAHR, back contacta of relay 6DSKNPR, and the winding of relay 6ECTR to negative terminalN of battery LB. Accordingly, normal 75 code of reverse 21, polaritywill be transmitted to section 6BT by relay 6ECTR.

At the cut section location CS, relay CETR will commence operating at a75 code rate and relay CEHR will pick up. Accordingly, a feed-back codeat a 75 code rate and initially of normal polarity will be transmittedto section 6BT by relay CWCTR and a normal 75 code of reverse polaritywill be transmitted to section 6AT by relay CECTR. At the intermediatesignal location IS, relay 4ETR will commence operating at a 75 code rateand relay 4EHR will pick up. Therefore, teed-back code at a 75 code rateand of reverse polarity will be transmitted to section 6AT, therebycausing relay CEVR to commence operating and relay CEVPR to pick up.When relay CEVPR picks up, its contact b changes the polarity of thefeed-back code being transmitted by relay CWCTR from normal to reverse,which is correct for the established eastbound trafiic. Due to decodingunit 180DU being supplied with 75 code, relay 4DR will remain released.If another train were to enter section 4T at this time, thereby causingrelays 4EVR and 4EVPR to release, signal 4R5 would display a yellowaspect due to energization of its yellow lamp Y by a circuit which maybe traced from the positive terminal B of battery LB, over reversecontact d of relay 4DSR, front contact e of relay 4EHR, back contact bof relay 4DR, yellow lamp Y of signal 4R8, back contact 7 of relay 4WHRand back contact c of relay 4EVPR to the negative terminal N of batteryLB. However, with no train in section 4T, signal 4RS will be dark due tothe fact that the above traced circuit will be open at back contact c ofrelay 4EVPR. Section 4T will be supplied with normal and feed-back codeat a 180 code rate of reverse polarity in a manner substantially thesame as that described for the apparatus when the stretch of track wasvacant and the apparatus was arranged for an eastbound train movement.

When the train vacates section 8T, the circuit arrangement will assumethe same condition it was in before the train movement started.

It should be clear that from the time signal 2RAS (or 2RBS) was clearedand during the time the train occupied any of the sections from 2T to8T, inclusive, it would have been impossible for the direction oftrafiic to be changed to westbound since upon attempting to change thedirection of traflic, the cascading of the polar relays would have beenforestalled either by the deenergization of one of the DSK relays or bythe fact that the polarities of the normal and feed-back codes wereopposite.

It should also be clear that it would make no difference in theoperation of my appaartus if the train were to use a passing sidingsince the section 2T includes a portion of the passing siding includingrails 3 and 4 and section 8T includes part of the passing sidingincluding rails 5 and 6.

From the foregoing description it should be apparent that my trackcircuit system would operate in a manner similar to that alreadydescribed regardless of how many intermediate signal locations were inthe circuit and regardless of how many cut sections were employedbecause these intermediate signal locations and cut sections merelycascade the action as illustrated with the cut section CS andintermediate signal location IS between sections 4T and ST. It should befurther pointed out that my system will operate just as well if no outsection were present and similarly it would operate if there were nointermediate signal locations present. If there were no cut sections inthe system the circuit arrangement at the intermediate location wouldcascade the action of the relay from one headblock to another directlyas it does now through the cut section, and if there were nointermediate signal location, then there would be a direct action fromone headblock to the other without the intermediate cascading of therelays.

Due to the symmetry of the circuit arrangement it is not deemednecessary to explain how the trafiic direction could be restored. to thenormal Westbound movement since the action would be substantiallysimilar to the description of the change of direction from westbound toeastbound which has already been made.

Although I have herein shown and described only one form of apparatusembodying my invention, it is to be understood that various changes, andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a stretch of railway track over which traific maymove in either direction, said stretch being divided into a plurality oftrack sections by insulated joints, said stretch being provided with afirst and second headblock signal at its respective ends, each tracksection being provided at each end with two polarized code followingtrack relays having their windings connected in series one beingresponsive to current of normal polarity and, the other being responsiveto current of reverse polarity, a plurality of code detecting relays,one associated with one each of said track relays and energized when itsassociated track relay is operating, each track section being providedat each end with a code transmitter for selectively actuating the trackrelays atthe other end of the track section, a traific directionselecting lever which may occupy a first and a second positioncorresponding to the direction of trafl-lc over the stretch, a polarizedtraffic direction relay at the junction of each two adjacent tracksections, means including said traffic selecting lever in its firstposition for actuating the code transmitter at thev first end of saidstretch to transmit normal code of normal polarity to the first, endsection, said normal code of normal polarity in said first end sectionactuating the track relay at the vend remote from the first end ofsaid'stretch responsive to currents of normal polarity and therebycausing its associated code detecting relay to pick up, means includingthe track relays and their associated code detecting relays at the endof each section remote from said first end for cascading said normalcode of normal polarity through the remaining sections of said secondend, said code transmitter in each section at the end remote from saidfirst end transmitting feed-back code of normal polarity during the offtime of said code transmitter transmitting normal code to the sectionand controlled by said track relays and their associated code followingrelays at the end remote from said first end, said feed-back code ofnormal polarity in each section actuating the track relay responsive toimpulses of normal polarity at the end of the section nearest said firstend of said stretch and thereby picking up its associated code detectingrelay, means including the track relays and their associated codedetecting relays at the second end of the stretch for conditioning saidheadblock signal at said second end of said stretch to display itsproceed aspect due to the presence of normal code of normal polarity insaid second end section, means including said traffic selecting lever inits second position for actuating said code transmitter at the first endof said stretch to transmit normal code of reverse polarity to saidfirst end section and thereby actuate the track relay responsive tocurrents of reverse polarity at the end of said first end section remotefrom said first end and pick up its associated code detecting relay,means including the track relays for each section at the end remote fromthe first end. of said stretch responsive to impulses of reversepolarity and their associated code detecting relays for cascading saidnormal code of reverse polarity through the remaining track sections tosaid second end of said stretch, means including said track relays andtheir associated code detecting relays at said second end of saidstretch and the traflic direction relays at said second end of saidstretch for causing said code transmitter at said second end to transmitfeed-back code of reverse polarity to the second end section, meansincluding the track relays in each section at the end remote from saidsecond end and their associated code detecting relays for cascading saidfeed-back code of reverse polarity through the remaining sections tosaid first end of said stretch, said reversal of polarity of said normaland feed-back codes throughout the stretch causing said trafiicdirection relays to reverse the tratfic direction and thereby cause saidsecond headblock to display its stop aspect and said first headblock tobe placed in a condition for displaying its proceed aspect.

2. In a two directional single track system of signaling, a tracksection provided with a track circuit at the entering end of the stretchof single track for a given direction of tratfic, means including atwo-position trafiic selector in its normal position for supplyingnormal code of normal polarity to said track circuit at the leaving endof said section, means including said trafiic selector in its reverseposition for supplying normal code to reverse polarity to said trackcircuit at the leaving end of said track section, means for supplyingfeed-back code of normal polarity during the off time of said normalcode at the entering end of said section provided said section and thesection immediately in advance of it are unoccupied, a first track relayoperating when said normal code is of normal polarity, a second trackrelay operating when said normal code is of reverse polarity, a polarstick trafiic direction relay, a polar stick auxiliary relay, saidauxiliary relay energized to its normal position only when said trafiicdirection relay occupies its normal position and said first track relayis operating, said auxiliary relay energized to its reverse positiononly when said second track relay is operating, said traffic directionrelay energized to its reverse position only when said auxiliary relayis reversed and said trafiic selector is reversed, and means effectiveupon the reversal of said traffic direction relay for reversing thepolarity of the feed-back code and thereby the direction of tratfic overthe stretch.

3. In a two-direction signaling system for a stretch of single trackrailway, the combination comprising, track circuit means for saidstretch, means including a twoposition trafiic selector means in itsnormal position for supplying normal code of a preselected polarity tosaid track circuit means at the exit end of said stretch for theselected'traific direction, means for supplying feedback code of thesame polarity to said track circuit means at. the entrance end of saidstretch, other means including said tramc direction selector means inits reverse position for supplying normal code of the opposite polarityto said track circuit means at said exit end, a pair of track relaysconnected to said track circuit means at said entrance end so as to beselectively responsive to the received normal track code, one beingoperable by code of said preselected polarity and the other by code ofsaid opposite polarity, a two-position traffic direction stick relay,circuit means including contacts of said track relays for energizingsaid trafiic direction relay to operate to its normal or to its reverseposition according to the position of said traific selector means andthe polarity of the received track code, said circuit means beingarranged to prevent the operation of said traffic relay while saidstretch is occupied to thereby provide directional locking, and meansactuated by said traific relay in its reverse position to reverse thepolarity of said feed-back code to thereby reverse the direction oftraffic through said stretch.

4. In a signaling system for a stretch of single trackmal code to saidtrack circuit means having a preselected polarity or the oppositepolarity according as said traffic selector means occupies its first orits second position respectively, a first and a second track relay atthe entrance end for the selected traffic direction selectivelyconnected to said track circuit means so that said first relay operateswhen the normal code has said preselected polarity and said second trackrelay operates when the normal code has said-opposite polarity, a polarstick traific direction relay means having a first and a second positioncorresponding to said first and said second positions of said trafiicselector means, a first circuit means including contacts of said firsttrack relay to energize said traffic relay means to operate to its firstposition, a second circuit means including cont-acts of said secondtrack relay to energize said trafiic relay to operate to its second position, coding means at said entrance end responsive to the operation ofsaid track relays and effective to supply feed-back code to said trackcircuit means during the otf period of said normal code, said feed-backcode being of said preselected polarity when said first track relay isoperating, and other circuit means actuated by the operation of saidtrafiic relay means to its reverse position when said traffic selectormeans occupies its reverse position to reverse the polarity of saidfeed-back code to said opposite polarity to thus reverse the selecteddirection of trafiic over said stretch.

S. In combination, along a stretch of railway track over which trafficmoves in either direction, said stretch being divided by insulatedjoints into a plurality of track sections, a first and a secondheadblock signal at a first and a second end of said stretchrespectively, a traffic direction selecting mean-s which may occupy afirst or a second position corresponding to selected direction oftrafiic over said stretch; a pair of code following track relays at eachend of each track section having connections to the section, a firsttrack relay of each pair being responsive to code of one relativepolarity and the second track relay being responsive to code of theopposite relative polarity; a code transmitting means at each end ofeach track section having connections to the corresponding section toactuate the track relays at the other end of that section; a pluralityof code detecting relays, one associated with each track relay andenergized when that associated track relay is operating; a first circuitmeans including said trafiic selecting means in its first position tocause the code transmitting means for the first section adjacent saidfirst end to transmit a normal code of said one polarity, a secondcircuit means including said trafiic selecting means in its secondposition to cause said first end code transmitting means to transmitnormal code of said opposite polarity, means including the track relaysand associated code detecting relays at the end of each section remotefrom said first end and the code transmitting means at the end of eachsection other than said first end section remote from said second end tocascade said normal code of either polarity throughthe remainingsections to said second end, the code transmitting means at the end ofeach section remote from said first end being actuated by the operationof said first track relay at the corresponding location to transmit afeedback code of said one polarity during the off period of said normalcode, means including the track relays at said second end of saidstretch for conditioning said second headblock signal to display itsproceed aspect only when the received normal code is of said onepolarity, a polar stick traflic direction relay at the junction of eachtwo adjacent track sections, a two-position traffic direction relaymeans at said second end of said stretch; means responsive to thereceipt of normal code of said opposite polarity at said second end andincluding the second track relay at that location, its associated codedetecting relay, and said trafiic direction relay means to actuate thecode transmitting means at said second end to transmit a feed-back codeof said opposite polarity to the track 25 section adjacent said secondend, means including said track relays and associated code detectingrelays at the end of each section remote from said second end to cascadesaid feed-back code of opposite polarity through the remaining sectionsto said first end, said reversal of polarity of the normal and feed-backcodes being effected only when said normal and said feed-back codesthroughout said stretch are of said one polarity at the time saidtraific selecting means is moved to its second position, the operationof said second track relays at the adjoining ends of each two adjacenttrack sections by said normal and said feed-back codes of saidoppositepolarity energizing their associated code detecting relays to cause thecorresponding trafiic direction relay to reverse position to 26 thusreverse the traffic direction through said stretch, and means eifectiveupon the reversal of said tratfic direction relay-s to halt the supplyof normal code to said first end section-and to initiate a supply ofnormal code of said opposite polarity to said second end section.

References Cited in the file of this patent UNITED STATES PATENTS Re.22,841 Shields Feb. 11, 1947 1,912,923 Thompson June 6, 1933 2,244,901Staples June 10, 1941 2,318,545 Van Horn May 4, 1943 2,357,240 Van HornAug. 29, 1944 2,430,314 Van Horn Nov. 4, 1947

